This invention relates to apparatus for supplying and controlling the flow of a liquid, particularly in a dust suppression system.
Prior art systems are known for suppressing dust in grain handling installations by spraying oil on the grain. In such a system, the grain is flowed in a steam, and oil in the form of small droplets is sprayed on the grain. The oil wets the grain including the dust particles and causes the particles to stick to the grain kernals. The oil is, of course, an edible form such as white mineral oil or soy bean oil. By suppressing the dust, the danger of an explosion is reduced, the working place is cleaner and healthier, air ventilation systems may be reduced, and the dust purchased with the grain is maintained in the grain.
In such an operation it is advantageous to be able to start and stop the flow of oil as abruptly as possible, in coordination with the starting and stopping of the stream of grain. If the oil starts to flow after the start of the stream of grain, some of the grain may be left unsprayed; if the grain stream stops but the oil dribbles for a time, there is a waste of the oil and perhaps some grain with excessive oil or a puddle of oil.
It has been difficult in prior art systems to abruptly stop the flow of oil. An on-off flow control valve could be connected in the line and turned off to stop the flow, but oil between the valve and the spray nozzle would slowly dribble out of the nozzle after the valve has been turned off.
A prior art system has been provided wherein a pump is used to develop oil pressure and a bidirectional electric motor drives the pump. To stop the oil flow, the direction of rotation of the motor and the pump is reversed, the purpose being to develop a reverse liquid flow in order to stop the oil spray. A problem with this system is that the electric power to the motor is turned off until the motor and the pump stop, and then the electric power (with opposite polarity) is turned on again to drive the motor-pump in the opposite direction. While this arrangement is an improvement over a system that relies on an on-off flow control valve, some oil still dribbles and is lost during the time that the motor-pump comes to a stop and then is powered again in the reverse direction.
It is a general object of the present invention to provide an improved system for controlling liquid flow, wherein the flow may be started or stopped more abruptly than in prior art systems.